Catheter-mounted ultrasonic transducers are known to the art, as described for example in U.S. Pat. No. 4,794,931 and 5,368,037. These catheter-mounted transducers are single use, disposable devices which provide a radial image format either by means of a radial phased array or a rotating crystal. These devices do not include any mechanism for steering or articulating the tip of the catheter. Because the catheter tip cannot be steered, it is in general not possible to position the transducer optimally to obtain different views of the tissue or structure being imaged.
Catheters other than ultrasonic imaging catheters currently exist which have articulating tips. One typical steering mechanism for such a catheter uses a knob which rotates about an axis perpendicular to the length of the catheter. As the user rotates the knob clockwise or counterclockwise, the tip of the catheter will articulate either up and down, or left and right. In addition to manipulating the catheter tip with the knob, the catheter is generally rotated within the vessel by rotating the control housing. Such rotation of the control housing causes the knob to rotate as well as the catheter, and can place the knob in an relatively inaccessible position for the user. Awkward positioning of the steering knob can make manipulating the catheter tip difficult.
Accisano U.S. Pat. No. 5,571,085 and Fleischhackor U.S. Pat. No. 5,395,329 disclose control handles for steerable catheters which utilize a rotating collar to move a slide longitudinally in the catheter handle. Steering lines are connected to the slide such that reciprocation of the slide steers the distal tip of the catheter. This arrangement provides the advantage of a steering actuator which extends around the complete circumference of the handle and rotates about the longitudinal axis of the handle.
The present invention is defined by the following claims, and nothing in this section should be taken as a limitation on those claims. By way of introduction, the preferred embodiments described below relate to controlling an ultrasonic transducer assembly.
In one preferred embodiment, a steering mechanism is provided for an ultrasonic transducer assembly of the type comprising an elongated conduit comprising a distal end portion and a proximal end portion, a plurality of ultrasonic transducer elements carried by the conduit adjacent the distal end portion, and at least one steering line carried by the conduit.
The steering mechanism comprises a housing defining a longitudinal axis extending generally parallel to the proximal portion of the conduit, an actuator such as a steering ring is carried by the housing for rotation about the longitudinal axis, and a steering hub mounted for rotation in the housing and coupled to the actuator such that rotation of the actuator with respect to the housing about the longitudinal axis causes rotation of the steering hub.
The steering line is secured adjacent the steering hub such that rotation of the steering hub alters the effective length of the steering line to steer the distal end of the conduit. Unlike other steering mechanisms in which the steering line is threaded through multiple holes and slots prior to termination to the steering hub, in the steering mechanism of this preferred embodiment, the steering line wraps at least partially around the diameter of a stator. This not only makes the steering mechanism easier to assemble, but it also reduces the amount of friction on the steering line.
In another preferred embodiment, a steerable, catheter-mounted ultrasonic transducer assembly is provided comprising an elongated conduit and a plurality of transducer elements as described above. A steering mechanism is coupled to the proximal portion of the conduit, and at least one steering line interconnects the steering mechanism and the distal end portion of the conduit. In one preferred embodiment, the steering line comprises a braided yarn spun from a liquid crystal polymer. In another preferred embodiment, the steering line comprises a liquid-crystal-polymer-extruded monofilament. Such steering lines can withstand high catheter processing temperatures and can withstand being under a load for an extended period of time without stretching.
In yet another preferred embodiment, the steering mechanism is part of a housing that removablely connects to a cable of a medical diagnostic ultrasonic imaging system. In this preferred embodiment, the housing comprise an extension portion to ensure that the portion of the housing that the user grips to manipulate the steering mechanism is sufficiently far away from the cable to ensure that the cable will remain sterile and thus reusable.
In an additional preferred embodiment, a controller for an ultrasonic transducer assembly is provided that is contoured to a human hand to provide a comfortable, efficient, and enjoyable one-handed operation of controls on the controller.
Though these preferred embodiments are preferably used together as described below, they can, if desired, be used independently of one another. For example, the preferred steering mechanism can be used with conventional, metal steering lines, and conversely the preferred steering lines can be used with conventional steering mechanisms with or without a housing with an extension portion.